Easel.



A. F. JOBKE.

EASEL.

APPLICATION FILED JUNE 10, 1918.

l ,28,607 Patented Dec. 24,. 1918.

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Application filed June 10, 1918.

To all whom it mayconcern:

Be it known that 1, AUGUST F. J OBKE, a citizen of the United States, residing at Detroit, in the county of Wayne and State of Michigan, have invented certain new and useful Improvements in Easels, of which the following is a specification.

My invention relates to easels and has for its subject an arrangement, which in a simple manner causes a sheet of flexible material, such as copying papers for photographic purposes or the like, to adhere to a plane surface for a certain length of time, which enables the material to receive the photographic or other impression intended, and enables the removal therefrom without any injury to the surface of the material, thereby saving not only the margin now sacrificed for the purpose of driving push pins or tacks through it, but also the effort and time required to properly fasten and remove it.

This object I obtain by the use of a moderate vacuum behind the flexible sheet, which is then pressed upon its support by the atmosphere with a relatively high pressure which corresponds directly to the area of the openings over which the flexible sheet extends, the support being so formed as to insure a perfectly fiat surface of the sheet, that a true reproduction may be possible on the same.

In describing my invention, reference may be had to the accompanying drawing, in which Figure 1 is a plane front view of the easel with the connection necessary to a vacuum producer, and Fig. 2 is a sectional side view of the same.

The easel proper consists of a fiat chamber made of sheet metal or other material, whose two principal dimensions correspond to the largest size of sheet to be fastened to it. The third dimension may be very small, and is determined by the flow of air through the hollow space when the vacuum is produced, after the sheet is laid over the front surface 11. The back surface 12 is a plate of solid material preventing any leakage of air through it.

The front surface is made perforated with holes of a suitable size, whose number the termines the actual pressure to be exerted, or it ma be some form of screen permitting practically the whole surface of the paper or other material to receive the atmospheric Specification of Letters Patent.

Patented Dec. as, rare,

Serial No. 239,337.

pressure with the exception of a small margin around the edge to prevent leakage of air into the inside of the easel, which would destroy the vacuum.

A vacuum pump 13, in the present case as shown, a water-jet pump, but which may as well be and in larger installations preferably is a reciprocating pump of suitable construction, is through a hose 14 connected with a. nipple leading to the inside of the easel. A vessel 15 may advantageously be connected with the hose line at a suitable point, since it helps through its volume quickly, to establish the vacuum back of the paper on the easel.

To maintain a constant vacuum through the working ofthe pump in the line and the vessel 15 a valve 16 ma be arranged between the individual easel and the vessel.

With a relatively small vacuum a paper laid over the front surface of the easel will adhere immediately, though there may he a moderate leakage under the edges, which will not be large enough to reduce the vacuum below the permissible degree. A slight lifting of one corner will expose enough of the perforations or screened surface to reduce the vacuum in the chamber to zero and thereby permit the sheet to drop 0d" freely. If the valve 16 is arranged as a check-valve, there will be only a slight drop of vacuum in the line during the moment of lifting the paper ofi.

While my invention may be exemplified by a simple easel to suit a single size of sheet, I show in the illustration an arrangement suitable for two difl'erent sizes. A greater variation may for the simplicity of the whole installation often be required, and would be arranged in a similar manner. The dividing line 17 represents a wall, separating air-tight the inner part, corresponding to the smaller size, from the outer part, which with the inner one together corresponds to the larger size of paper. As shown, the compartments thus formed are symmetrical to a common center line normal to the faces of the chamber, which arrangement provides foran easy centering with a camera, and is advantageous in reproduction. The nipple 18 may lead through the wall 17 to the inner part and is permanently connected thereto. Through a valve 19 in the wall or in the connection with the nipple a communication between the inner and outer part can be established which will change the extent of the vacuum between the larger and smaller areas. 1

Having thus described my invention, what I claim is:

1. As an easel for flexible material used in the graphic arts a'flat chamber having a perforated face plate and solid back plate and sides, Wallsnormal to these plates, dividing the chamber into compartments to suit flexible sheets of different sizes, an airduct from the source of a vacuum to the compartment suiting the smallest size sheet, and a valve adapted to connect or separate two compartments from each other, enabling the establishment of a vacuum by placing a flexiblesheet of corresponding size on the perforated face plate.

naeaeoa 2. As an easel for flexible material used in the graphic arts a flat chamber having a perforated face plate and solid back plate and sides, walls normal to these plates, dividing the chamber into inner and outer compartments, arranged symmetrically to a common center'line to suit flexible sheets of different sizes, an air-duct from the source of a vacuum to the compartment suiting the smallest size sheet, and a valve adapted to connect or separate two compartments from each other, enabling the establishment of a vacuum by placing a flexible sheet ofcorresponding size on the perforated face plate.

In testimony whereof l afiix my signature this sixth day of June A. D. 1918.

AUGUSTF. JOBKE. 

